In an attempt to alter the toxicity/activity relationships of psychoactive drugs that contain certain heterocyclic aromatic nuclei, their structure will be altered by introduction of a methylene bridge in such a way that aromaticity will be preserved in the homoaromatic sense. The chemical modifications will be applied first to model compounds containing indole, isoindole, carbazole, fluorene, quinoline, isoquinoline and pyridine rings. Subsequently the chemical information will be applied to the physiologically active molecules. The modified species will have chemical and physical characteristics that may also provide information about their mode of action, since the introduction of the methanobridge will alter the planarity of the system and subsequently the interaction with active biological sites because of the presence of the protruding methylene group. Aromaticity will likely be retained, and verification will readily be obtained through the use of nuclear magnetic resonance studies. The same experimental data will be used to determine whether or not all products and intermediate species exist in a closed-ring (norcaradiene) or open-ring (cycloheptatriene) form.